Project Summary Direct oxidation and functionalization of C?H bonds, though ubiquitous in Nature?s biosynthetic machinery, have only recently gained traction as a viable strategy in chemical synthesis. Despite remarkable advances, contemporary chemical methods for C?H oxidation still face significant challenges in achieving useful levels of selectivity on complex scaffolds. In contrast, the oxidative enzymes that have evolved to perform these transformations are capable of achieving unprecedented levels of selectivity. However, studies on these enzymes have mainly focused on their mechanistic features, and very little attention has been given to their applications in organic synthesis. This proposal seeks to bridge the gap between organic synthesis and mechanistic enzymology and establish a novel paradigm in complex molecule synthesis by integrating Nature?s repertoire of oxidative biocatalysts into the synthetic organic toolbox. We contend that a synergistic interplay between chemo- and biocatalytic methods will lead to unsurpassed levels of efficiency in accessing clinically- relevant small molecules. As a proof-of-principle demonstration, we have recently completed preliminary investigations that illustrate the viability of this chemoenzymatic strategy in the preparation of small natural products and valuable building blocks with therapeutic potential. Building on this success, this proposal aims to demonstrate the universality of this strategy in the efficient and practical syntheses of two medicinally relevant natural product scaffolds. Significant elements of innovation in this work include (1) the discovery of previously uncharacterized enzymes with novel activities from various secondary metabolite biosynthetic pathways, (2) the pursuit of new strategies for optimizing their catalytic efficiencies, and (3) the identification of appropriate avenues to demonstrate their applications in chemical synthesis. Though there are significant challenges associated with this project, its scientific impacts will be far-reaching. If successful, our ability to strategically incorporate enzymatic functionalizations into the design of complex molecule synthesis will stimulate the development of new logic in chemical synthesis centered on the use of Nature?s biocatalytic repertoire, radically altering the way chemists? approach synthetic planning. Thus, new small molecule therapeutics can be prepared in a more efficient and practical manner.